Because I don't have two 3DS's I'm having to get Pokemon such as Alakazam and Scizor in my nature of choice and EV trained appropriately by the GTS as I do have both X and Y now. Unfortunately it does not let you offer Pokemon holding any sort of Mega Stone.

Which leads me on to my questions. Will you be able to transfer Pokemon holding Mega Stones to the PokeBank and if you get one subscription to PokeBank does it count it for the DS console or for the game, in other words will I have to buy PokeBank twice for X & Y once the free trial is up in January?

Edit

Thanks for the answers.
So is there anyway to trade Mega Stones between X & Y with just one 3DS or is it impossible?